# Technical Introduction

### Inverter test setup <a href="#toc170750861" id="toc170750861"></a>

Following block diagram gives an overview of a typical inverter test setup from the point of view of a single device under test (DUT):

<figure><img src="https://2885081809-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FASow5OW3r2Iqc4FrSPHd%2Fuploads%2FYAu8iB5s3D8vjqDh4FRn%2F11.png?alt=media" alt=""><figcaption></figcaption></figure>

The central item in the picture is the inverter, the device under test (DUT), which is electrically connected to:

* Power supplies, communication interfaces, miscellaneous sensors
* The HV battery
* the electrical motor via typically 3 motor phases
* and its position sensor
* For inverters for power ranges of several kilowatts water cooling is usually applied.
*

The yellow marked parts are covered by the IRS EME active motor load:

* synchronous motor
* position sensor
* and partially the HV battery in combination with a standard DC power supply.

### Test approaches for motor load <a href="#toc170750862" id="toc170750862"></a>

#### Classic mechanical coupled motors, passive load, high-end motor emulator <a href="#toc170750863" id="toc170750863"></a>

To simulate the motor, there are generally different approaches commonly used:

* Simulation of a simple passive load
* Operation of a real motor, mechanically coupled with another motor-inverter-combination
* High-end motor simulators

The following table shows the advantages and disadvantages of these setups:

| Passive coil                                                   | Active motor simulator – full size                                    | Mechanically coupled motors                                                                           |
| -------------------------------------------------------------- | --------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------- |
| <mark style="color:green;">✅ Very cost-efficient</mark>        | <mark style="color:red;">⛔️ Very high price</mark>                    | <mark style="color:red;">⛔️ Very high price</mark>                                                    |
| <mark style="color:green;">✅ Small setup</mark>                | <mark style="color:red;">⛔️ Space consuming setup</mark>              | <mark style="color:red;">⛔️ Space consuming setup</mark>                                              |
| <mark style="color:green;">✅ Full phase current</mark>         | <mark style="color:green;">✅ Full phase current</mark>                | <mark style="color:green;">✅ Full phase current</mark>                                                |
| <mark style="color:red;">⛔️ Only reactive phase current</mark> | <mark style="color:green;">✅ Simulation of real phase currents</mark> | <mark style="color:green;">✅ Simulation of real phase currents</mark>                                 |
| <mark style="color:red;">⛔️ No recuperation</mark>             | <mark style="color:green;">✅ Recuperation possible</mark>             | <mark style="color:green;">✅ Recuperation possible</mark>                                             |
| <mark style="color:orange;">🔶 Low DC currents</mark>          | <mark style="color:red;">🔶 Real DC current from battery</mark>       | <mark style="color:orange;">🔶</mark> <mark style="color:orange;">Real DC current from battery</mark> |

#### IRS EME Active motor load as intermediate solution <a href="#toc170750864" id="toc170750864"></a>

IRS EME active motor load is a solution which combines advantages of full-size high end motor simulators with the advantages of the passive coil, by keeping the concept simple, reliable and at a low cost.

| Active motor simulator – IRS                                          |
| --------------------------------------------------------------------- |
| <mark style="color:orange;">🔶 Cost efficient</mark>                  |
| <mark style="color:green;">✅ Small setup</mark>                       |
| <mark style="color:green;">✅ Full phase current</mark>                |
| <mark style="color:green;">✅ Simulation of real phase currents</mark> |
| <mark style="color:green;">✅ Recuperation possible</mark>             |
| <mark style="color:green;">✅ Real DC current, but low power</mark>    |

To simulate a real load condition the induced voltage of the electrical motor needs to be generated, according to the equivalent circuit of a motor:

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Voltage sources for high power are often also switched power supplies, while a good energy feedback is necessary to achieve a compact and cost-efficient setup.

### IRS EME basic principle of operation. <a href="#toc170750865" id="toc170750865"></a>

Following picture shows the basic setup of the IRS electrical motor emulator for a three-phase-inverter as device under test (DUT):

<figure><img src="https://2885081809-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FASow5OW3r2Iqc4FrSPHd%2Fuploads%2FQNdQmUiHjHnBkvn2GJzl%2Feme-principle.png?alt=media&#x26;token=4ad6cc03-1b1e-4533-81a5-164080f31de2" alt=""><figcaption></figcaption></figure>

The concept is based on the idea to directly couple two inverters and run against each other - both three phases and the DC-Link are directly coupled. As battery simulator a standard power supply may be used. With appropriate control of the motor simulator, the phase current flows from DUT to simulator via the phase coils and back to the DUT via the DC-Link, and vice versa.

Thus, the DC-Link of the DUT is stressed with a realistic current, but since the energy is flowing between the two inverters, the battery simulation needs only to provide the energy for the losses of the entire system. This is one of the most important benefits: a relatively small power supply without energy feedback to the grid can be used. With a power supply of only 20kW,

* 250kW can be simulated at 500V DC voltage,
* 350kW can be simulated at 850V DC.

The standard emulator variant is capable of handling voltages up to 1000V, resulting in even higher power ranges which can be simulated. In most setups, three basic setpoints define the operation:

* EME generates the induced voltage of the motor
* DUT is in current control mode, defining the applied torque to the motor.
* EME defines the speed via the position sensor signal

In this document, we mostly refer to the voltage range up to 1000V, since this is covered by the standard IRS EME. In the meantime, different downsized variants are available which will be illustrated in later chapters. But the basic principle is the same for all IRS EME variants.